Flat card having internal relief and incorporating at least one electronic element

ABSTRACT

A card ( 1 ) including a lower layer ( 2 ) and a layer ( 4 ) of solidified binder ( 6 ) in which various elements are incorporated, in particular a coil ( 12 ) electrically coupled to an electronic unit ( 8 ). The coil ( 12 ) exhibits a lower planar surface ( 30 ), the inner face ( 20 ) of the lower layer ( 2 ) exhibiting a relief ( 18 ) defining sunken valleys traversing said inner face ( 20 ).

FIELD OF THE INVENTION

The present invention concerns electronic cards incorporating at leastone electronic element.

In particular, a card according to the invention comprises an integratedcircuit serving for example for the identification of persons.

BACKGROUND OF THE INVENTION

A category of electronic cards concerned by the invention is made up bycards without exterior electrical contact and possessing a coil enablingelectromagnetic coupling with an external arrangement.

By card is understood every object having a substantially planarstructure defining a general plane of the object and exhibiting anycontour whatsoever in such general plane.

The patent document EP 0 570 784 in the name of the present applicantdescribes various embodiments of an electronic card comprising a layerformed by a solidified binder in which is incorporated at least oneelectronic element electrically coupled to a coil. This document alsodescribes various embodiments of a method of manufacture of such a card.

In a particularly advantageous embodiment, there is provided apositioning structure exhibiting at least one principal opening in whichis housed the electronic element. In each embodiment described, the coiland the electronic element are housed within such principal opening. Inall the proposed embodiments, the various elements incorporated withinthe solidified layer of binder are located facing entirely planarsurfaces.

According to an embodiment of the method of manufacture described in thepatent document EP 0 570 784, the following various steps for themanufacture of a card are provided:

I) the bringing onto a work surface of a first outer layer formed from asolid material;

II) the placing of at least one electronic element on the first outerlayer;

III) the bringing of a binder onto the first outer layer;

IV) the bringing onto said binder of a second outer layer formed from asolid material and facing the first outer layer;

V) the application of a pressure on the first and second outer layersuntil such outer layers are located at a predetermined distance relativeto one another.

In a final step, the binder is solidified in order to form anintermediate layer between the outer layers.

According to a specific characteristic of the method describedhereinbefore, a positioning structure, defining at least one internalzone serving in particular for positioning the coil, is brought inbetween steps I and IV of the method.

According to a variant of the method described hereinbefore, it isforeseen to bring initially the planar outer layer and the variouselements to be incorporated into the card, in particular the electronicelement electrically coupled to the coil and also a positioningstructure when the latter is provided. Next, the binder is applied inthe form of a viscous liquid. Onto such binder is then applied thesecond outer layer. Finally, with the help of pressing means, pressureis exerted on the outer layers and consequently on the binder along adirection perpendicular to the work surface so as to form the layer ofbinder in which are incorporated various elements as provided.

The variant of the method described hereinbefore is very advantageousfrom an economic viewpoint since it enables producing large quantitiesof cards at low cost. Additionally, such variant is advantageous fromthe fact that it does not necessitate applying heat in order to melt theouter layers, thus avoiding the shrinkage phenomena of the material andbuckling of the card once cooled. However, the applicant has observed inthe course of numerous experiments that the method describedhereinbefore brings results which are satisfactory for various specificembodiments, but that on the other hand a certain number of cardsobtained by this method and having one of the structures proposed inpatent document EP 0 570 784 does not exhibit a sufficientlysatisfactory flatness such that for certain embodiments the industrialyield is relatively low.

Effectively, the requirement of flatness for electronic cards isparticularly high, in particular when printing is provided on anexternal surface of such cards. Certain printing techniques requireabsolutely planar outer surfaces, lacking which deformations appear inthe printed message.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the drawbacksremaining in the invention described in patent document EP 0 570 784 inproviding an electronic card exhibiting very good flatness and noresidual air in the binder layer, such card also being obtainable withthe help of a relatively simple method.

Here it should be mentioned that the applicant has carried out extensiveresearch on the cards produced according to the method describedhereinbefore in order to detect the nature of the problem causingdeformations in the surface of a certain number of cards. During suchresearch, the applicant has initially determined that in a certainnumber of applications the coil occupied a relatively large surface asprojected into the general plane of the card. Next, and in contrast tothe coils as shown drawn on the figures of patent document EP 0 570 784,the coils used in electronic cards generally exhibit a cross-section ofrectangular form. Additionally, such coils are self-supporting, that isto say, the windings of such coils are glued to one another. Thus, thecoil exhibits a definite form and a certain rigidity.

In the variant of the method described hereinbefore, when the coil isapplied to the first planar outer layer, the lower surface of such coilthen bears against the inner face of such first outer layer. When thebinder is applied in the form of a viscous liquid and pressure isexerted on the latter, the binder spreads out and covers the uppersurface of the coil, which generates a resultant pressure on such coiltowards the work surface. The coil is thus pressed against the firstouter layer and the binder does not infiltrate between the coil and suchfirst outer layer. Thereby, the first outer layer does not adhere to thelayer of binder on its superposition surface with the coil, which canbring about deformations on the surface of the first outer layerfollowing solidification of the binder and removal of the pressureexerted on the latter.

The above-mentioned problem is further aggravated by a second problemconnected with the state of the lower surface of the coil. Effectively,the coil is formed from windings exhibiting a circular cross-section.The coils are formed with the help of a winding arrangement generallyexhibiting two flanges between which the coil is formed. Inevitably, thesurfaces of the coil exhibit a multitude of furrows, certain of whichmay have a depth which is not negligible. Once the coil is brought ontothe inner face of the outer layer, the furrows located on the lowersurface of the coil define at least one substantially closed spacebetween the coil and the outer layer, resulting in a confinement of airduring formation of the card. Such residual air can be slightlypressurized during the application of pressure on the binder serving toform the binder layer which brings about deformations of the outer faceof the outer layer when application of the pressure has ceased.Additionally, it has been observed that when said pressure is removed,the residual air confined between the coil and the outer layer is apt todiffuse within the card and in particular at the interface between theouter layer initially supplied and the layer of binder.

It will be mentioned that similar problems appear with other elementsincorporated in an electronic card, in particular when a substrate isprovided on which the electronic element is secured, such as thatdescribed on FIGS. 10 and 11 of patent document EP 0 570 784. Suchproblems can also be encountered with other elements incorporated in thecard, for example with an electronic unit of a certain dimensionexhibiting a planar face or a protection ring on the interior of whichis housed an integrated circuit for example.

In order to achieve the purpose of the invention in resolving theabove-mentioned problems, the invention has as object a card comprisingan element having a first surface substantially planar or exhibiting atleast one external cavity which can be substantially closed by ageometric plane, a first layer of solid material and a second layerformed by a solidified binder in which said element is immersed. Thefirst layer exhibits a first inner face to which the solidified binderadheres. Such card is characterized in that the first inner faceexhibits a relief provided at least in the interior of a first zonecomprising the surface of superposition between said first surface ofsaid element and said first inner face, such relief defining sunkenvalleys traversing said first zone.

The card according to the invention exhibits at least two importantadvantages. Firstly, the relief provided on the inner face of the firstlayer assures proper evacuation of all residual air during manufactureof the card with the help of a viscous liquid binder applied onto thevarious elements incorporated in said card. Secondly, such card permitsthe binder, applied in the form of a viscous liquid, to be correctlyinfiltrated between said first surface of said element incorporated inthe second layer and the inner face of said first layer. According to avariant embodiment, the totality of the inner face of the first layerexhibits a relief defining sunken valleys traversing said inner face.

According to a variant embodiment, a third layer is provided arranged sothat the second layer forms an intermediate layer between the first andthird layers.

According to another embodiment, in addition to said element, there isprovided a positioning structure for such element within the layer ofbinder.

Other characteristics and advantages of the present invention will bestill better described with the help of the following description madewith reference to the annexed drawings representing non-limitingexamples.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of a first embodiment of an electroniccard according to the invention;

FIG. 2 shows schematically one embodiment of a method of manufacture ofthe card shown on FIG. 1;

FIG. 3 is a cross-section view of a first variant of the firstembodiment;

FIG. 4 is a view along the section line IV—IV of FIG. 3;

FIG. 5 is a cross-section view of a second variant of the firstembodiment;

FIG. 6 is a view along the section line VI—VI of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

With the help of FIGS. 1 and 2, there will hereinafter be described afirst embodiment of an electronic card according to the invention aswell as an embodiment of a method of manufacture of such card.

On FIG. 1, card 1 basically comprises three layers, namely a first layer2 formed from a solid material, in particular a synthetic plasticmaterial, a second layer 4 formed from a solidified binder 6 in whichvarious elements are immersed, namely an electronic unit 8 housed in theinterior of a protection ring 10 and electrically coupled to a coil 12serving as a magnetic coupling with an external communication unit, notshown. Furthermore, in layer 4, there is provided a positioningstructure 14 serving to position coil 12 and the electronic unit 8 inthe interior of the card. In particular, the positioning structure 14serves to define an internal zone within binder layer 4 for coil 12 andthe electronic unit 8. The usefulness of such positioning structure hasalready been described in patent document EP 0 570 784 and will onceagain be specified in the description of the embodiment of the methodaccording to the present invention.

Card 1 further comprises a third layer 16 formed from solid material,for example a plastic material. Binder 6 is chosen so that, oncesolidified, it exhibits good adhesion to the material used for layers 2and 16. According to an essential characteristic of the invention, arelief 18 is provided on the inner face 20 of the first layer 2.According to a special characteristic of the invention, the inner face22 of layer 16 has a relief 24 substantially identical to the relief 18.It will be further noted that layers 2 and 16 respectively comprise twoplanar outer faces 26 and 28 onto which a printed message can beprovided.

The positioning structure 14 shows, for example, a configuration similarto any one of the configurations provided in patent document EP 0 570784. Coil 12 has a cross-section of rectangular form and exhibits afirst surface 30 and a second surface 32 which are substantially planarand located respectively facing the inner faces 20 and 22 of layers 2and 16. Here it will be mentioned that the entire inner faces 20 and 22are respectively covered over by the reliefs 18 and 24. Thus, inparticular, the superposition zone of face 20 of the layer 2 with thesurface 30 of coil 12 shows a relief. The structure of the relief isprovided in a manner such that this relief exhibits sunken valleysentirely traversing said superposition zone. Two special variants forthe relief provided on faces 20 and 22 will be described with the helpof FIGS. 4 and 6.

On FIG. 2 is schematically shown a particularly advantageous andundemanding method of manufacture for card 1. The method of manufactureaccording to the invention comprises the following consecutive steps:

I) the bringing onto a work surface 40 of the first layer 2 exhibitingon its inner face 20 the relief 18 hereinbefore described. The outerface 26 is placed on the planar work surface 40, the inner face 20 beinglocated on the side opposite such work surface 40;

II) the bringing onto the internal face 20 of the positioning structure14 which exhibits a principal opening 42 into which are next brought thecoil 12 and the electronic unit 8 located on the interior of theprotection ring 10;

III) the bringing in of a binder 6 in the form of a viscous liquid in aquantity sufficient to form layer 4 of card 1;

IV) the bringing in of the second outer layer 16 onto the binder 6 in amanner such that the inner face 22 exhibiting relief 24 is located onthe side of binder 6;

V) the application of pressure on the outer face 28 of layer 16 andconsequently on binder 6 in the viscous liquid state so that such binder6 spreads out uniformly between the two outer layers 2 and 16 in orderto form an intermediate layer of predetermined height;

VI) the hardening of binder 6 to form the second layer 4 of card 1.

During step VI pressure directed perpendicularly to the work surface 40will be advantageously maintained. It will be noted that, withoutdeparting from the framework of the present invention, the molecularstructure and/or the composition of binder 6 can vary between the liquidstate in which it is brought in and the final solid state.

Thanks to the relief 18 provided on the inner face 20 of the first outerlayer 2, the various elements brought in, in particular coil 12 and thepositioning frame 14 cannot be applied against the inner face 20 so asto prevent the infiltration of binder 6 or to retain residual airbetween the outer projections defining external cavities, in particularon surface 30 of coil 12 during step V in which pressure is exerted soas to distribute binder 6 uniformly between the two outer layers 2 and16. Effectively, relief 18, exhibiting sunken valleys traversing theinternal face 20, the binder can readily penetrate between the lowersurfaces of the incorporated elements and the internal face 20 whichthus assures good adhesion of the various layers of the card andevacuation of all residual air, damaging for the flatness of the card.

It will be mentioned that binder 6 being applied subsequently to thebringing in of the various elements incorporated in layer 4, such binder6 spreads out more easily on the upper surfaces of the various elementsincorporated in layer 4, in particular the surface 32 of coil 12. Thisis all the more so that the quantity of binder 6 applied is greater thanthe quantity of binder finally forming layer 4. However, in the case inwhich the height of one of the incorporated elements, in particular coil12, is substantially equal to the predetermined height of theintermediate layer 4 and given the presence of relief 18 on face 20 oflayer 2, it can happen that such elements rise up slightly duringapplication of a pressure and come to bear against the inner face 22 ofthe second outer layer 16. To avoid this, it has been provided that theinner face 22 of layer 16 also exhibits a relief 24 similar to relief18.

It will be noted that the method here described can be practised in anenvironment having a certain degree of vacuum. Furthermore, the pressureexerted on the binder can be provided by various means, in particular aflat press, one or several rolling cylinders.

With the help of FIGS. 3 and 4, there will be briefly describedhereinafter a variant of the embodiment of a card according to theinvention.

Card 51 comprises a layer 2, identical to that of card 1, comprising inparticular an inner face 20 exhibiting a relief 18. Card 51 furthercomprises a layer 54 formed from a solidified binder 6 in which isincorporated a coil 12 electrically coupled to an electronic unit 58.Coil 12 and the electronic unit 58 are entirely immersed in the binder 6of layer 54.

On FIG. 4 is shown a plan view according to section line IV—IV of FIG.3, binder 6 not being shown in order to permit a partial view of theinner face 20 exhibiting relief 18. Such relief is formed by a set ofsmall blocks 60 of little height. Thus, the relief 18 defines sunkenvalleys between the set of such blocks 60, such valleys traversingentirely the inner face 20 of the outer layer 2 and defining multiplepaths for infiltration of binder 6 and evacuation of the residual airduring the process of manufacture of the card described hereinbefore. Byway of example, relief 18 is a relief impressed by conventionalimpression techniques or formed by embossing layer 2.

With the help of FIGS. 5 and 6, there will be briefly describedhereinafter a second variant embodiment of a card according to theinvention.

Card 6 comprises a first outer layer 62, a second outer layer 64 and anintermediate layer 66 formed by a solidified binder 6. In the interiorof layer 66 is incorporated a coil 12 and an electronic unit 8 arrangedon the face 68 of a substrate 70. On such face 68 is also partiallyarranged the coil 12. Substrate 70 serves in particular to define theposition of unit 8 relative to the coil 12 and also serves as anelectric inter-connection support between such unit 8 and coil 12.

Substrate 70 is located on the side of layer 62, the planar face 72 ofsuch substrate being located facing the inner face 74 of layer 62 whichexhibits a relief 76 defining a set of pyramids 78 of comparativelylittle height relative to the height of the layer 66. It will bementioned that during the process of manufacture of card 61, layer 62 isinitially brought onto the work surface. Next, binder 6 is applied oncethe assembly formed by coil 12, unit 8 and support 70 has been placed onlayer 62.

Again, in the plan view of FIG. 6 according to the section line VI—VI ofFIG. 5, binder 6 has not been shown so as to show up the relief 76 andthe assembly formed by coil 12, unit 8 and substrate 70. By way ofexample, relief 76 is obtained by knurling or by die stamping layer 62.

Relief 76 defines sunken valleys traversing the inner face 74 of layer62. Furthermore, such a relief minimizes the contact surface between theincorporated elements and the inner face 74 if such incorporatedelements are arranged to bear against relief 76.

As has already been mentioned, the importance of the presence of arelief is essential on the outer lower layer initially brought in duringthe process of manufacture of a card according to the invention. Thepresence of such a relief on the inner face of the upper layer isadvantageous and enables guaranteeing a perfectly planar card.Nevertheless, the numerous experiments carried out have shown that therelief provided on the inner face of the upper layer was notindispensable in a certain number of cards manufactured according to theprocess of the invention. What is more, in certain embodiments, it canhappen that the incorporated elements exhibit only a singlesubstantially planar face located facing the lower layer.

In other terms, the relief provided on the inner face of the lower layerplays an essential role when the incorporated elements exhibit at leastone substantially planar lower surface or exhibit external cavitieslocated between the external projections against which a geometric planecan be bearing so as to close substantially such cavities. Next, whenthe incorporated elements exhibit at least one substantially planarupper surface, it is generally advantageous also to provide a relief onthe inner face of the upper outer layer. This latter relief is that muchmore advantageous when the element or elements exhibiting a planar uppersurface have a height less than, but substantially equal to the heightof the layer formed by the solidified binder in which they areincorporated.

For reasons of security and industrial yield, it is neverthelesspreferable to provide a relief on each of the two respective inner facesof the two outer layers.

Finally, it will be mentioned that binder 6 applied in the form of aviscous liquid is preferably chosen in a manner such that it can beapplied at a relatively low temperature, in particular at ambienttemperature. By way of example, the binder is constituted by a resinknown to persons skilled in the art. Among such resins can be mentionedepoxy resin and two-components glues.

What is claimed is:
 1. A card comprising: at least one electronicelement, a first layer formed from a solid material and having a firstinner face, and a second layer formed by a solidified binder in whichsaid electronic element is located and which adheres to the first innerface of said first layer, wherein said first inner face exhibits arelief provided at least on the interior of a first zone on which theelectronic element is located, said relief defining sunken valleystraversing said first zone.
 2. The card of claim 1, further comprising athird layer having a second inner face to which said solidified binderof said second layer adheres, such third layer being arranged in amanner such that said second layer forms an intermediate layer betweensaid first and third layers.
 3. The card of claim claim 2, in which saidelectronic element has a second surface that is substantially planar orexhibits at least one external cavity which can be substantially closedby a geometric plane, wherein said second inner face exhibits a reliefprovided at least on the interior of a second zone comprising thesurface of superposition with said second surface of said electronicelement, such relief defining sunken valleys traversing said secondzone.
 4. The card of claim 1, wherein said electronic element isconstituted by a coil exhibiting a substantially rectangular crosssection, such coil being electrically coupled to an electronic unit. 5.The card of claim 1, wherein said electronic element is constituted by arigid protection ring surrounding an electronic unit.
 6. The card ofclaim 1, wherein said electronic element is formed by a substrate onwhich an electronic unit is fixedly arranged.
 7. The card of claim 1,wherein said electronic element is formed by an electronic unit.
 8. Thecard of claim 1, wherein said relief is formed by an indentation made onan initially planar surface of said first layer.
 9. The card of claim 1,wherein said relief is obtained by knurling, by stamping, or byembossing said first layer.
 10. A card comprising: at least oneelectronic element, a first layer formed from a solid material andhaving a first inner face, and a second layer formed by a solidifiedbinder in which said electronic element is located and which adheres tothe first inner face of said first layer, wherein the totality of saidfirst inner face exhibits a relief so that the interior of a first zoneon which the electronic element is located is provided with said relief,said relief defining sunken valleys traversing entirely said first zone.11. The card of claim 10, further comprising a third layer having asecond inner face to which said solidified binder of said second layeradheres, such third layer being arranged in a manner such that saidsecond layer forms an intermediate layer between said first and thirdlayers.
 12. The card of claim 11, in which said electronic element has asecond surface that is substantially planar or exhibits at least oneexternal cavity which can be substantially closed by a geometric plane,wherein said second inner face exhibits a relief provided at least onthe interior of a second zone comprising the surface of superpositionwith said second surface of said electronic element, such reliefdefining sunken valleys traversing said second zone.
 13. The card ofclaim 10, wherein said electronic element is constituted by a coilexhibiting a substantially rectangular cross section, such coil beingelectrically coupled to an electronic unit.
 14. The card of claim 10,wherein said electronic element is constituted by a rigid protectionring surrounding an electronic unit.
 15. The card of claim 10, whereinsaid electronic element is formed by a substrate on which an electronicunit is fixedly arranged.
 16. The card of claim 10, wherein saidelectronic element is formed by an electronic unit.
 17. The card ofclaim 10, wherein said relief is formed by an indentation made on aninitially planar surface of said first layer.
 18. The card of claim 10,wherein said relief is obtained by knurling, by stamping, or byembossing said first layer.
 19. A card comprising: a first layer formedfrom a solid material and having a first inner face exhibiting a reliefon an interior of a first zone, said relief defining sunken valleystraversing said first zone; a second layer formed by a solidifiablebinder material which adheres to said first inner face; and, anelectronic element disposed within said second layer so as to overlaysaid sunken valleys, said electronic element having a first surfacefacing said first layer, said first surface having a configuration thatdoes not match the relief exhibited by said first inner face so thatspaces exist between said first surface and said first inner face, saidsunken valleys providing paths through which said solidifiable bindermaterial fills said spaces.